- The kinetics, stereochemistry, and deuterium isotope effects in the α-pinene pyrolysis. Evidence for incursion of multiple conformations of a diradical
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Pyrolysis of optically active α-pinene gave 95% racemic limonene (dipentene), alloocimine, racemic α-pinene, α-pyronene. Activation parameters are reported. Pyrolysis of (S) syn-6-trideuteriomethyl α-pinene at 256.7°C for 2400s gave dipentene with twice as much deuterium as hydrogen transfer with kH/kD=1.49 and alloocimine with a Z and E trideuteriomethyl ratio of ca. 5 with kH/kD=0.89. The isotope effect on loss of starting material was 1.16. Separation of the enantiomers of α-pinene from 3600s pyrolyses at 256.7°C followed by NMR analysis revealed that the ratio of the R-syn to R-anti to S-anti isomers is 4.6:3.7:1 at roughly two half-lives. Kinetic analysis reveals that the previously proposed mechanism for all conversions involving slow interconversion of two diradicals with Cs symmetry is not consistent with the distribution of the ??-pinene isomers, particularly the formation of more suprafacial-retention product (R-anti) than bond-rotated isomer (S-anti). Inclusion of another Cs species (ignoring the deuteriums) that would be intermediate between the originally proposed Cs species, appears more consistent with the observations.
- Gajewski, Joseph J,Kuchuk, Ilya,Hawkins, Christopher,Stine, Robert
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p. 6943 - 6950
(2007/10/03)
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- Reductive Deoxygenation of α,β-Unsatured Ketones via Cyanophosphates by Lithium in Liquid Ammonia
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A new method for deoxygenation of α,β-unsatured ketones via cyanophosphates by lithium metal in liquid ammonia is described
- Yoneda, Ryuji,Osaki, Hirotaka,Harusawa, Shinya,Kurihara, Takushi
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p. 2817 - 2818
(2007/10/02)
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